This invention relates to a traffic information processing apparatus used for navigation.
A system is available to distribute traffic information to in-vehicle navigation systems. On the other hand, an in-vehicle navigation system is available to search for the route shortest in travel time using the traffic information received (JP-A-2002-372430).
In the presence of a plurality of traffic information from different sources, the simultaneous use of the plurality of the traffic information as they are by the navigation system may lead to an inconvenience. Consider an exemplary case in which a sensor (vehicle detector) installed on a road collects traffic information (referred to as “the installed sensor-originated traffic information) on the one hand and a vehicle actually running on a road collects traffic information (referred to as “the probe car-originated traffic information) on the other hand. The installed sensor-originated traffic information contains the traffic information around the clock. These traffic information, however, are limited to those on the road on which the particular sensor is installed. Since the sizes of vehicles are not uniform, a detection error makes the installed sensor-originated traffic information not always accurate. The probe car-originated traffic information, on the other hand, not only may contain the information on the roads not installed with the sensor, but reflects the propensities of each driver and therefore may not always be an average one. The information in the name of “traffic information”, therefore, have various features. A plurality of traffic information for the same time zone on the same road may be discrepant to some degree. The use of the plurality of discrepant traffic information as they are may pose the problem described below.
Assume that, as shown in FIG. 16, only the installed sensor-originated traffic information (such as derived from VICS (vehicle information and communication system)) are available for links A, B, C, while only the probe car-originated traffic information can be used for links D, E, F. Also assume that the probe car-originated traffic information tends to be shorter in link travel time and that the route shortest in travel time is searched for using the link travel time of the two traffic information as they are. Then, a route Y including a detour passing through the links D, E, F, instead of a route X straight along a road, may be retrieved. Frequent sessions of this search may result in the retrieval of a route having many curves.